The foundation is not just the base on which a building stands; it is also the most important structure element. It supports the weight of the walls and roof and the contents of a building. It also prevents moisture from damaging a home.
A foundation (or, more commonly, base) is the element of an architectural structure that connects it to the ground and transfers loads from the structure to the ground. Foundations are generally considered either shallow or deep. Foundation engineering is the application of soil mechanics and rock mechanics (Geotechnical engineering) in the design of foundation elements of structures.
Shallow foundations are used when there is no deep excavation or when a building has a very light load. They are usually less than 6 ft deep and consist of masonry or concrete. Shallow foundations transfer the load from the walls or columns to the soil so that it does not cause excessive settlement or shear failure in the soil.
Deep foundations are used when a layer of weak soil is at the surface. They are used to support very large buildings, bridges, and offshore structures built on soft clay or sand deposits. Deep foundations can be made out of reinforced concrete piles, steel H-piles, steel pipe piles, timber piles, and precast concrete piles.